Gastra base won't work with NP extension.
There seems to be a difference of about 1 mm from groove to base.
All brands are a little different.
This variance is a problem.
Some combos have the weight pushing on the groove , this is not good.
The weight should be on the flat and the groove only for the odd upward force.
When clicking in pin make sure base and extension are touching properly.
Thats my two cents worth